Anthracite-based silicon-carbon composite negative electrode material and preparation method thereof
The preparation of anthracite-based silicon-carbon composite anode material solves the problems of insufficient energy density and high cost of existing lithium-ion battery anode materials, enabling the application of high-energy-density and low-cost lithium-ion battery anode materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 山西华阳集团新能股份有限公司
- Filing Date
- 2024-01-05
- Publication Date
- 2026-08-04
AI Technical Summary
The specific capacity of existing graphite carbon materials for lithium-ion batteries is close to the theoretical limit, which cannot meet the requirements of high energy density. Silicon-carbon composite materials have problems such as high expansion coefficient, short cycle life, poor conductivity and high preparation cost.
The anthracite-based silicon-carbon composite anode material is prepared by combining ultra-low ash anthracite and high-purity nano-silicon. The high-temperature graphitization process is omitted during the preparation process. Photovoltaic waste silicon is used as the silicon source. Wet ball milling and spray drying technologies are used to form a structure with an ultra-low ash anthracite matrix as the core and a carbon coating layer as the outer shell.
It effectively suppressed the volume expansion of silicon, improved the conductivity and structural stability of the material, reduced the preparation cost, and improved the specific capacity and cycle performance, thus meeting the demand for high energy density lithium-ion batteries.
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Figure CN117936733B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of anode material technology, and more specifically, to an anthracite-based silicon-carbon composite anode material and its preparation method. Background Technology
[0002] In recent years, with the booming development of new energy vehicles and the continuous expansion of the energy storage market, the demand for lithium-ion batteries has been increasing, especially for high-energy, long-life, high-safety, and low-cost lithium-ion batteries. The goal is to achieve a battery energy density of 400Wh / kg by 2025 and 500Wh / kg by 2030. To achieve this goal, in addition to improving battery structure and increasing the energy density of electrode materials, upgrading and replacing material systems is urgently needed!
[0003] Currently, commercially available lithium-ion batteries primarily use graphite carbon materials as anodes, with actual specific capacities ranging from 360-365 mAh / g, already very close to their theoretical limit of 372 mAh / g. There is no room for further improvement, failing to meet the demand for increased energy density in lithium-ion batteries, necessitating the development of a new generation of high-capacity anode materials. Among numerous developed material systems, silicon boasts a theoretical specific capacity as high as 4200 mAh / g, more than 10 times that of existing commercial graphite carbon anodes. It exhibits excellent energy density and fast-charging performance and is gradually developing into the next generation of high-performance lithium-ion battery anode materials. However, in practical applications, it still faces challenges such as high expansion coefficient (lithium insertion / extraction volume change > 300%), short cycle life, and poor conductivity. Common strategies to improve the cycle stability of silicon anodes include nanostructuring, surface coating, compositing with inert materials, and alloying. Among these, compositing carbon materials with silicon is one of the most effective ways to suppress volume expansion and improve conductivity.
[0004] Existing silicon-carbon composite anode materials typically use graphite, carbon nanotubes / nanofibers, and graphene as carbon sources, resulting in high material preparation costs. Chinese invention publication CN112142060A, titled "A Coal-Based Silicon-Carbon Composite Anode Material," describes a preparation method using high-temperature graphitized anthracite as the carbon source and diatomaceous earth as the silicon source. This method involves a lengthy process and high energy consumption. Extensive acid treatment is used in the pretreatment of both anthracite and diatomaceous earth, requiring stringent reaction conditions and resulting in poor environmental benefits. Furthermore, this invention adds lithium powder to the composite material for pre-lithiation to improve initial efficiency, leading to higher composite material preparation costs. Therefore, developing a silicon-carbon composite material for lithium batteries with excellent electrochemical performance, a short process flow, low manufacturing cost, and ease of industrialization is a key technical challenge in this field. Summary of the Invention
[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one aspect of the present invention is to provide anthracite-based silicon-carbon composite anode material, wherein the composite anode material comprises, by weight percentage, 5%-50% high-purity nano-silicon, 50%-90% anthracite-based carbon material, and 5%-15% carbon coating layer; the composite anode material has a two-layer structure, with an embedded core layer and a coating layer.
[0006] Preferably, the anthracite-based carbon material is ultra-low ash anthracite, and the high-purity nano-silicon is obtained through photovoltaic waste silicon treatment.
[0007] Preferably, the core is an anthracite-based carbon material with high-purity nano-silicon uniformly attached to its surface, and the outer shell is a carbon coating layer.
[0008] Another objective of this invention is to provide a method for preparing anthracite-based silicon-carbon composite anode material, the specific steps of which are as follows:
[0009] S1. Anthracite is purified and ball-milled to obtain ultra-low ash anthracite, and photovoltaic waste silicon is pretreated to obtain high-purity nano-silicon;
[0010] S2. Place the high-purity nano-silicon in S1 in a dispersant, ultrasonically vibrate until uniform, add a binder solution, stir until uniform, add ultra-low ash anthracite, wet ball mill until uniformly dispersed, spray dry and granulate to obtain a uniformly mixed anthracite-based silicon-carbon composite material.
[0011] S3. The anthracite-based silicon-carbon composite material obtained in S2 is added to the pyrolytic carbon precursor solution, stirred at high speed and mixed evenly, and then dried. The dried composite material is carbonized at high temperature in an inert environment to obtain the anthracite-based silicon-carbon composite anode material.
[0012] Preferably, the purification and ball milling steps in S1 are as follows: after the anthracite is crushed and screened to determine its particle size, it is subjected to gravity separation, flotation, drying, and ball milling to obtain ultra-low ash anthracite.
[0013] Preferably, in step S1, the anthracite raw material is crushed to a particle size of less than 200 mesh, and the particle size of the anthracite is controlled to D50 of 5μm-25μm, most preferably 5μm-15μm, by ball milling to obtain ultra-low ash anthracite.
[0014] Preferably, the photovoltaic waste silicon pretreatment step in S1 is as follows: after the silicon powder is ball-milled and crushed, it is acid-washed, water-washed and dried to obtain high-purity silicon powder, and after wet high-energy ball milling, it is heat-treated under an inert atmosphere to obtain high-purity nano-silicon.
[0015] Preferably, in step S1, the photovoltaic waste silicon is ball-milled once to reduce the particle size to submicron level, then acid-washed with concentrated hydrochloric acid (36%-38% by volume) at a liquid-to-solid ratio of 2:1 at room temperature for 6 hours. After acid washing, it is washed with water until the pH of the washing solution is near neutral, dried, and then subjected to a second wet high-energy ball milling. The wet high-energy ball milling solvent is one or more combinations of alcohols, ketones, alkanes, and esters; most preferably, it is one or more combinations of ethanol, acetone, and isopropanol. The ball milling jar is made of stainless steel, zirconium oxide, or ceramic, most preferably zirconium oxide. The high-energy ball milling speed is 100 rpm-1100 rpm, and the ball milling time is 10 h-30 h. The resulting D50 particle size is 80 nm-250 nm, most preferably 80 nm-150 nm. The powder is then heat-treated in an inert atmosphere at 500℃-700℃ to obtain high-purity nano-silicon.
[0016] Preferably, the dispersant in S2 is methanol, ethanol, propanol, isopropanol, butanol, or acetone; the mass ratio of high-purity nanoparticles to dispersant is 1:10-1:20; the ultrasonic vibration time is 0.5h-2h; the binder solution includes a binder and a binder solvent; the binder is one or more combinations of coal tar, coal pitch, polyvinyl alcohol, phenolic resin, and epoxy resin; the binder solvent is water, ethanol, methanol, ethylene glycol, glycerol, acetone, ethyl acetate, or diethyl ether; the concentration of the binder solution is 20%, and the amount of binder solution added is 2-5 times the mass of the nano-silicon; the stirring speed of the mixer is 1000rpm-2000rpm, and the time is 2h; the amount of ultra-low ash anthracite added is 1-5 times the mass of the nano-silicon; the wet ball milling granulation particle size is 1μm-25μm; the inlet air temperature of the spray drying is 150℃-260℃, the outlet air temperature is 80℃-150℃, and the time is 30min.
[0017] Preferably, in step S3, the mass ratio of the anthracite-based silicon composite material to the pyrolytic carbon precursor solution is 1:1 to 1:5; the concentration of the pyrolytic carbon precursor solution is 2% to 10%; the pyrolytic carbon precursor solution includes a pyrolytic carbon precursor and a pyrolytic carbon precursor solvent; the pyrolytic carbon precursor is one or more combinations of asphalt, citric acid, glucose, or phenolic resin; the pyrolytic carbon precursor solvent includes water, alcohols, esters, or ethers; and the high-speed stirring speed is 1000 rpm to 2000 rpm. m, time is 1h-5h; drying time is 10h, temperature is 80℃-120℃; the carbonization process is carried out at high temperature under nitrogen atmosphere, the temperature is raised to 900℃-1300℃ at a rate of 10℃-15℃, the most preferred is 900℃-1100℃, held for 6h-9h, after the heat preservation is completed, it is naturally cooled to room temperature, and the anthracite-based silicon-carbon composite material is obtained by grinding. The composite material D50 particle size is 10μm-20μm, the most preferred is 10μm-15μm.
[0018] The beneficial effects of this invention are as follows:
[0019] This invention provides an anthracite-based silicon-carbon composite anode material, comprising an outer shell and a core. Ultra-low ash anthracite, as the matrix material, exhibits excellent conductivity and a low expansion rate. Through the action of a binder, high-purity nano-silicon is tightly bonded to the ultra-low ash anthracite matrix, effectively suppressing the volume expansion of silicon during lithium insertion / extraction.
[0020] This invention produces anthracite-based silicon-carbon composite material using wet ball milling and spray drying, with high-purity nano-silicon uniformly dispersed within ultra-low ash anthracite. Simultaneously, a uniform outer layer of soft carbon material provides transport channels and a supporting framework for electrons and ions, which improves the material's conductivity and structural stability, and enhances its cycle performance.
[0021] This invention uses ultra-low ash anthracite as a carbon source. Compared to the graphite, carbon nanotubes / nanofibers, and graphene commonly used in existing silicon-carbon composite anode materials, it eliminates the need for high-temperature graphitization or carbonization of the raw coal, significantly reducing energy consumption. Furthermore, it avoids acid washing for deashing during the pretreatment of the ultra-low ash anthracite, which is beneficial for industrial production. This invention also uses photovoltaic waste silicon as a silicon source, obtaining high-purity nano-silicon after pretreatment, thus reducing raw material costs.
[0022] Compared with existing graphite-based silicon-carbon composite materials, the anthracite-based silicon-carbon composite anode material provided by this invention has a shorter process flow, lower manufacturing cost, and excellent electrochemical performance, exhibiting higher specific capacity, first coulombic efficiency, and cycle performance.
[0023] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. Attached Figure Description
[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:
[0025] Figure 1 This is a schematic diagram of the structure of the anthracite-based silicon-carbon composite anode material of the present invention;
[0026] Figure 2 This is a SEM image of the anthracite-based silicon-carbon composite anode material according to Embodiment 1 of the present invention;
[0027] Figure 3 This is a charge-discharge cycle curve of the anthracite-based silicon-carbon composite anode material according to Embodiment 1 of the present invention.
[0028] in, Figure 1 The correspondence between the reference numerals and component names in the attached drawings is as follows:
[0029] (1) is a carbon coating layer, (2) is high-purity nano-silicon, and (3) is ultra-low ash anthracite. Detailed Implementation
[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.
[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.
[0032] Example 1
[0033] (1) Anthracite pretreatment: Anthracite is crushed and sieved, and coal powder with a mesh size of less than 200 is taken. A heavy liquid with a suitable density is prepared, and the upper layer of suspended clean coal is taken. The obtained clean coal is flotated and dried with reagents to obtain low-ash anthracite. The obtained low-ash anthracite is added to a ball mill, the speed is set to 800 rpm, and after 2 hours of treatment, ultra-low ash anthracite with a D50 particle size of 5μm-25μm is obtained.
[0034] Pretreatment of photovoltaic waste silicon: After a first ordinary ball milling, the particle size of photovoltaic waste silicon is reduced to the submicron level. The ball milling speed is 300 rpm and the ball milling time is 10 h. The ball milled material is then acid washed and water washed. Concentrated hydrochloric acid (volume fraction 36-38%) is used for acid washing. The liquid-solid ratio is 2:1 at room temperature and the acid washing time is 6 h. After acid washing, the material is washed with water multiple times until the pH of the washing solution is close to neutral. After drying, a second high-energy ball milling is performed. The ball milling speed is 800 rpm and the ball milling time is 20 h. The obtained powder is heat-treated at 700℃ under a nitrogen atmosphere to obtain high-purity nano silicon with a D50 particle size of 100 nm.
[0035] (2) Take 20g of high-purity nano-silicon and add it to 200g of anhydrous ethanol. Sonicate for 30min to obtain a uniformly dispersed nano-silicon suspension. Dissolve 20g of phenolic resin in 80g of acetone and add it to the above suspension. Stir in a high-speed mixer at 1000rpm for 2h. Add the resulting mixed solution to a ball mill and add 80g of ultra-low ash anthracite. Control the ball mill speed at 300rpm and the ball milling time at 5h to obtain a uniformly dispersed silicon / anthracite slurry. Spray dry the above slurry with an inlet air temperature of 180℃, an outlet air temperature of 80℃, and a time of 30min to obtain anthracite-based silicon composite material with a particle size of 10μm.
[0036] (3) Dissolve 5g of citric acid in 100g of ethanol, add 50g of anthracite-based silicon composite material to the citric acid solution, stir in a high-speed mixer at 1000rpm for 2h, mix evenly, and then dry for 10h at 80℃. The dried composite material is then heated to 900℃ under a nitrogen atmosphere at a rate of 10℃ / min for high-temperature carbonization, held for 6h, and then naturally cooled to room temperature before grinding to obtain anthracite-based silicon-carbon composite anode material with a particle size of 10-15μm.
[0037] Example 2
[0038] (1) Anthracite pretreatment: Anthracite is crushed and sieved, and coal powder with a mesh size of less than 300 is taken. A heavy liquid with a suitable density is prepared, and the upper layer of suspended clean coal is taken. The obtained clean coal is flotated and dried with reagents to obtain low-ash anthracite. The obtained low-ash anthracite is added to a ball mill, the speed is set to 500 rpm, and after 2 hours of treatment, ultra-low ash anthracite with a D50 particle size of 5μm-25μm is obtained.
[0039] Pretreatment of photovoltaic waste silicon: After a first ordinary ball milling, the particle size of photovoltaic waste silicon is reduced to the submicron level. The ball milling speed is 300 rpm and the ball milling time is 10 hours. The ball milled material is then acid-washed and water-washed. Concentrated hydrochloric acid (volume fraction 36-38%) is used for acid washing. The liquid-solid ratio is 2:1 at room temperature and the acid washing time is 6 hours. After acid washing, the material is washed with water multiple times until the pH of the washing solution is close to neutral. After drying, a second high-energy ball milling is performed. The ball milling speed is 1000 rpm and the ball milling time is 20 hours. The obtained powder is heat-treated at 700℃ under a nitrogen atmosphere to obtain high-purity nano-silicon with a D50 particle size of 80 nm.
[0040] (2) 30g of high-purity nano-silicon was added to 500g of anhydrous ethanol and ultrasonically vibrated for 50min to obtain a uniformly dispersed nano-silicon suspension. 30g of epoxy resin was dissolved in 120g of ethyl acetate and added to the above suspension. The mixture was stirred in a high-speed mixer at 1500rpm for 2h. The resulting mixed solution was added to a ball mill, along with 80g of ultra-low ash anthracite. The ball mill speed was controlled at 500rpm, and the milling time was 5h to obtain a uniformly dispersed silicon / anthracite slurry. The slurry was spray-dried with an inlet air temperature of 200℃, an outlet air temperature of 80℃, and a time of 30min to obtain anthracite-based silicon composite material with a particle size of 15μm.
[0041] (3) Dissolve 10g of gluconic acid in 200g of water, add 70g of anthracite-based silicon composite material to the glucose solution, stir in a high-speed mixer at 1000rpm for 1h, mix evenly, and then dry for 10h at 110℃. The dried composite material is then heated to 1000℃ under a nitrogen atmosphere at a rate of 15℃ / min for high-temperature carbonization, kept for 9h, and then naturally cooled to room temperature before grinding to obtain anthracite-based silicon-carbon composite anode material with a particle size of 10μm-15μm.
[0042] Example 3
[0043] (1) Anthracite pretreatment: Anthracite is crushed and sieved, and coal powder with a mesh size of less than 250 is taken. A heavy liquid with a suitable density is prepared, and the upper layer of suspended clean coal is taken. The obtained clean coal is flotated and dried with reagents to obtain low-ash anthracite. The obtained low-ash anthracite is added to a ball mill, the speed is set to 600 rpm, and after 2 hours of treatment, ultra-low ash anthracite with a D50 particle size of 5μm-25μm is obtained.
[0044] Pretreatment of photovoltaic waste silicon: After a first ordinary ball milling, the particle size of photovoltaic waste silicon is reduced to the submicron level. The ball milling speed is 300 rpm and the ball milling time is 10 h. The ball milled material is then acid washed and water washed. Concentrated hydrochloric acid (volume fraction 36-38%) is used for acid washing. The liquid-solid ratio is 2:1 at room temperature and the acid washing time is 6 h. After acid washing, the material is washed with water multiple times until the pH of the washing solution is close to neutral. After drying, a second high-energy ball milling is performed. The ball milling speed is 800 rpm and the ball milling time is 20 h. The obtained powder is heat-treated at 700℃ under a nitrogen atmosphere to obtain high-purity nano silicon with a D50 particle size of 100 nm.
[0045] (2) Take 50g of high-purity nano-silicon and add it to 1000g of anhydrous ethanol. Sonicate for 80min to obtain a uniformly dispersed nano-silicon suspension. Dissolve 20g of polyvinyl alcohol in the above suspension and stir in a high-speed mixer at 1000rpm for 2h. Add the resulting mixed solution to a ball mill and add 50g of ultra-low ash anthracite. Control the ball mill speed at 300rpm and the ball milling time at 5h to obtain a uniformly dispersed silicon / anthracite slurry. Spray dry the above slurry with an inlet air temperature of 150℃, an outlet air temperature of 100℃, and a time of 30min to obtain anthracite-based silicon composite material with a particle size of 5μm.
[0046] (3) Disperse 5g of asphalt in 100g of petroleum ether, add 100g of anthracite-based silicon composite material to the asphalt solution, stir in a high-speed mixer at 2000rpm for 5h, and after mixing evenly, dry for 10h at 80℃. Carbonize the dried composite material at 1100℃ under nitrogen atmosphere at a rate of 15℃ / min, retain for 9h, and then grind after naturally cooling to room temperature to obtain anthracite-based silicon-carbon composite anode material with a particle size of 10μm-15μm.
[0047] Comparative Example
[0048] (1) Anthracite pretreatment: Anthracite is crushed and sieved, and coal powder with a mesh size of less than 200 is taken. A heavy liquid of appropriate density is prepared, and the upper suspended clean coal is taken. The obtained clean coal is then subjected to flotation and drying with reagents to obtain low-ash anthracite. The obtained low-ash anthracite is heated to 1200℃ at a rate of 10℃ / min and held for 3 hours. Subsequently, the temperature is increased to 3000℃ at the same rate and held for 10 hours. Then, it is cooled to room temperature and ground to obtain the desired graphitized anthracite.
[0049] Pretreatment of photovoltaic waste silicon: After a first ordinary ball milling, the particle size of photovoltaic waste silicon is reduced to the submicron level. The ball milling speed is 300 rpm and the ball milling time is 10 h. The ball milled material is then acid washed and water washed. Concentrated hydrochloric acid (volume fraction 36-38%) is used for acid washing. The liquid-solid ratio is 2:1 at room temperature and the acid washing time is 6 h. After acid washing, the material is washed with water multiple times until the pH of the washing solution is close to neutral. After drying, a second high-energy ball milling is performed. The ball milling speed is 800 rpm and the ball milling time is 20 h. The obtained powder is heat-treated at 700℃ under a nitrogen atmosphere to obtain high-purity nano silicon with a D50 particle size of 100 nm.
[0050] (2) Take 20g of high-purity nano-silicon and add it to 200g of anhydrous ethanol. Sonicate for 30min to obtain a uniformly dispersed nano-silicon suspension. Dissolve 20g of phenolic resin in 80g of acetone and add it to the above suspension. Stir in a high-speed mixer at 1000rpm for 2h. Add the resulting mixed solution to a ball mill and add 80g of ultra-low ash anthracite. Control the ball mill speed at 300rpm and the ball milling time at 5h to obtain a uniformly dispersed silicon / anthracite slurry. Spray dry the above slurry with an inlet air temperature of 180℃, an outlet air temperature of 80℃, and a time of 30min to obtain anthracite-based silicon composite material with a particle size of 10μm.
[0051] (3) Dissolve 5g of citric acid in 100g of ethanol, add 50g of anthracite-based silicon composite material to the citric acid solution, stir in a high-speed mixer at 1000rpm for 2h, mix evenly, and then dry for 10h at 80℃. The dried composite material is then heated to 900℃ under a nitrogen atmosphere at a rate of 10℃ / min for high-temperature carbonization, held for 6h, and then naturally cooled to room temperature before grinding to obtain anthracite-based silicon-carbon composite anode material with a particle size of 10-15μm.
[0052] The anthracite-based silicon-carbon composite anode material prepared in the above examples and comparative examples was mixed with an aqueous solution of binder PAA and conductive agent Super P (active component: binder: conductive agent = 91:6:3), and prepared into a paste in a homogenizer. This paste was then uniformly coated onto copper foil. The anode sheet was then vacuum dried, rolled, and cut into sheets. Using a lithium metal sheet as the counter electrode, a 1 mol / L LiPF6 solution of EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (EC:DMC:EMC = 1:1:1, with 5% FEC (fluoroethylene carbonate) added) as the electrolyte, and microporous polypropylene as the separator, a CR2032 simulated battery was assembled in a vacuum glove box. Charge-discharge cycle tests were conducted at room temperature using the LAND battery testing system from Wuhan Jinno Electronics Co., Ltd. The test conditions were: charge-discharge rate of 0.1C, voltage range of 0.005V-1.5V. The test results are shown in Table 1 below.
[0053] Table 1. Electrochemical test results of composite anode materials
[0054]
[0055] As shown in Table 1, the silicon-carbon composite material prepared by high-temperature graphitization of the comparative anthracite showed a decrease in initial reversible capacity and an increase in initial coulombic efficiency compared to Example 1. This is because anthracite, without high-temperature treatment, has a relatively higher number of heteroatoms and defects on its surface, and a higher specific surface area, providing more lithium storage active sites, which is beneficial to improving specific capacity.
[0056] The present invention provides a smokeless coal-based silicon-carbon composite anode material, the structural schematic diagram of which is shown below. Figure 1 As shown. Figure 2 Here is a SEM image of the anthracite-based silicon-carbon composite anode material from Example 1. Figure 3 This is a charge-discharge cycle curve of the anthracite-based silicon-carbon composite anode material in Example 1. Anthracite, as the matrix material, is tightly bonded to nano-silicon powder, effectively suppressing the volume expansion of silicon during lithium insertion / extraction. The composite material exhibits excellent conductivity and a low expansion rate. Simultaneously, the uniform outer layer of soft carbon material provides transport channels and a supporting framework for electrons and ions, which is beneficial for improving the material's conductivity and structural stability, and thus enhancing cycle performance. This invention uses ultra-low ash anthracite as the carbon source and photovoltaic waste silicon as the silicon source. Compared to existing graphite-based silicon-carbon composite anode materials, it eliminates the need for high-temperature graphitization or carbonization of the raw coal, shortening the process flow, significantly reducing raw material costs and energy consumption, and exhibiting excellent electrochemical performance with high specific capacity, initial coulombic efficiency, and cycle performance.
[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.
Claims
1. A method for preparing anthracite-based silicon-carbon composite anode material, characterized in that: The specific steps of the preparation method are as follows: S1. Anthracite is purified and ball-milled to obtain ultra-low ash anthracite, and photovoltaic waste silicon is pretreated to obtain high-purity nano-silicon; S2. Place the high-purity nano-silicon in S1 in a dispersant, ultrasonically vibrate until uniform, add a binder solution, stir until uniform, add ultra-low ash anthracite, wet ball mill until uniformly dispersed, spray dry and granulate to obtain a uniformly mixed anthracite-based silicon-carbon composite material. S3. The anthracite-based silicon-carbon composite material obtained in S2 is added to the pyrolytic carbon precursor solution, stirred at high speed and mixed evenly, and then dried. The dried composite material is carbonized at high temperature in an inert environment to obtain the anthracite-based silicon-carbon composite anode material. The composite anode material comprises, by weight percentage, 5%-50% high-purity nano-silicon, 50%-90% anthracite-based carbon material, and 5%-15% carbon coating layer; the composite anode material has a two-layer structure, with an embedded core layer and a coating layer on the outer shell. The anthracite-based carbon material is ultra-low ash anthracite, and the high-purity nano-silicon is obtained through photovoltaic waste silicon treatment. The core is an anthracite-based carbon material with high-purity nano-silicon uniformly attached to its surface, and the outer shell is a carbon coating layer.
2. The method for preparing anthracite-based silicon-carbon composite anode material according to claim 1, characterized in that: The purification and ball milling steps in S1 are as follows: after the anthracite is crushed and screened to determine its particle size, it is subjected to gravity separation, flotation, drying, and ball milling to obtain ultra-low ash anthracite.
3. The method for preparing anthracite-based silicon-carbon composite anode material according to claim 2, characterized in that: The anthracite raw material in S1 has a particle size of less than 200 mesh after crushing. The particle size of the anthracite is controlled to be 5μm-25μm by ball milling to obtain ultra-low ash anthracite.
4. The method for preparing anthracite-based silicon-carbon composite anode material according to claim 1, characterized in that: The photovoltaic waste silicon pretreatment step in S1 is as follows: after the silicon powder is ball-milled and crushed, it is acid-washed, water-washed and dried to obtain high-purity silicon powder. After wet high-energy ball milling, it is heat-treated under an inert atmosphere to obtain high-purity nano-silicon.
5. The method for preparing anthracite-based silicon-carbon composite anode material according to claim 4, characterized in that: In step S1, the photovoltaic waste silicon is ball-milled once to reduce the particle size to submicron level. It is then acid-washed with concentrated hydrochloric acid (36%-38% by volume) at a liquid-to-solid ratio of 2:1 at room temperature for 6 hours. After acid washing, it is washed with water until the pH of the washing solution is near neutral. After drying, it undergoes a second wet high-energy ball milling. The wet high-energy ball milling solvent is one or a combination of alcohols, ketones, alkanes, and esters. The ball milling jar is made of stainless steel or ceramic. The high-energy ball milling speed is 100-1100 rpm, and the milling time is 10-30 hours. The resulting powder with a D50 particle size of 80nm-250nm is then heat-treated at 500℃-700℃ in an inert atmosphere to obtain high-purity nano-silicon.
6. The method for preparing anthracite-based silicon-carbon composite anode material according to claim 1, characterized in that: The dispersant in S2 is methanol, ethanol, propanol, isopropanol, butanol, or acetone; the mass ratio of high-purity nanoparticles to dispersant is 1:10-1:20; the ultrasonic oscillation time is 0.5h-2h; the binder solution includes a binder and a binder solvent; the binder is one or more combinations of coal tar, coal pitch, polyvinyl alcohol, phenolic resin, and epoxy resin; the binder solvent is water, ethanol, methanol, ethylene glycol, glycerol, acetone, ethyl acetate, or diethyl ether; the concentration of the binder solution is 20%, and the amount of binder solution added is 2-5 times the mass of the nano-silicon; the stirring rate is 1000rpm-2000rpm, and the time is 2h; the amount of ultra-low ash anthracite added is 1-5 times the mass of the nano-silicon; the wet ball milling granulation particle size is 1μm-25μm; the inlet air temperature of the spray drying is 150℃-260℃, the outlet air temperature is 80℃-150℃, and the time is 30min.
7. The method for preparing anthracite-based silicon-carbon composite anode material according to claim 1, characterized in that: The mass ratio of the anthracite-based silicon-carbon composite material to the pyrolytic carbon precursor solution in S3 is 1:1-1:5; the concentration of the pyrolytic carbon precursor solution is 2%-10%; the pyrolytic carbon precursor solution includes the pyrolytic carbon precursor and the pyrolytic carbon precursor solvent; the pyrolytic carbon precursor is one or more combinations of asphalt, citric acid, glucose, or phenolic resin; the pyrolytic carbon precursor solvent includes water, alcohols, esters, or ethers; the high-speed stirring speed is 1000rpm-2000rpm, and the time is 1h-5h; the drying time is 10h, and the temperature is 80℃-120℃; the carbonization process is carried out at high temperature under a nitrogen atmosphere, with the temperature increased at a rate of 10℃-15℃ to 900℃-1300℃, held for 6h-9h, and then naturally cooled to room temperature after the holding period. The anthracite-based silicon-carbon composite material is obtained by grinding, and the D50 particle size of the composite material is 10μm-20μm.